The methods described in the prior art for the application of sheet-like jointing means onto a contact area of a wafer essentially take place as follows.
The sheet-like jointing means are usually multi-layer films with a middle layer, which provides for the jointing of the carrier wafer with the product wafer. Protective films are arranged above and below this middle layer, in order that the multi-layer films can be used in a space-saving manner during delivery and processing and the middle layer does not become jointed to itself and consequently could no longer be unrolled. These protective films also have the purpose of preventing contamination of the middle film.
With the generic methods, the multi-layer film is first guided to the carrier wafer. Along this path, the lower protective film is removed in order that the middle layer, also referred to as the adhesive film, can be brought into contact with the wafer. The carrier wafer—also referred to as the handling wafer—is made from very hard material, e.g. sapphire. Once the film has been brought onto the carrier wafer, a blade is used to cut along the edge of the carrier wafer, so that the carrier wafer and the film, now consisting solely of the middle layer and upper layer, are jointed without overlapping portions.
The carrier wafer thus obtained with the applied film is then introduced for further processing into known bonding systems, in which the upper protective layer is removed and the product wafer is bonded with the carrier wafer.
The critical point in the methods previously described in the prior art is the cutting of the sheet-like jointing means along the edge of the very hard carrier wafer. If a blade is used for this, the latter already has to be replaced after a few passes, because it is blunt. This thus causes high material wear and downtimes with the equipment.
If, on the other hand, a laser beam is used for cutting the film along the edge, the latter produces at the cutting edge a projecting border or bead, which subsequently hinders precise bonding.
When cutting along the edge, moreover, as soon as the blade has been conveyed once around the wafer, film stripes arise with inaccurate cutting, which then hang out from the wafer face during further processing and can even get onto the wafer surface.